The present invention relates to a method of producing metal composite materials such as cemented carbide.
U.S. Pat. No. 5,505,902 discloses a method in which one or more metal salts of at least one iron group metal containing organic groups are dissolved in at least one polar solvent such as ethanol, methanol, water and complex bound with at least one complex former comprising functional groups in the form of OH or NR3, (Rxe2x95x90H or alkyl). Hard constituent powder and, optionally, a soluble carbon source are added to the solution. The solvent is evaporated and the remaining powder is heat treated in an inert and/or reducing atmosphere. As a result, hard constituent powder coated with at least one iron group metal is obtained which, after the addition of a pressing agent, can be compacted and sintered according to standard practice, to form a body containing hard constituents in a binder phase. A disadvantage with the mentioned method is that the solution generally contains rather low amounts of the iron group metal which leads to large volumes of solution and thus long evaporation times when coating hard constituent powders with high binder content. Therefore, a hard constituent powder containing less than 5% binder phase is generally made and to this powder is added more binder metal powder to the desired final composition. This requires an additional process step and rather careful mixing in order to obtain an even microstructure.
It is an object of this invention to avoid or alleviate the problems of the prior art.
It is further an object of this invention to provide a method of producing metal composite materials such as cemented carbide.
It is an aspect of the invention to provide a method of making a hard constituent powder mixture containing at least one iron group metal comprising the following steps:
forming a solution by dissolving at least one salt of at least one iron group metal containing organic groups in at least one polar solvent and complex binding with at least one complex former comprising functional groups in the form of OH or NR3, where (Rxe2x95x90H or alkyl);
suspending in the solution at least one insoluble, reducible salt of at least one iron group metal;
adding hard constituent powder to the solution;
forming a powder mass by evaporating the solvent; and
heat treating the powder mass in an inert and/or reducing atmosphere to obtain a powder mixture.